As the Legislature convened in Montpelier last week for the start of a new biennium, Vermont’s lawmakers braced themselves for a full agenda. Whether it’s a moratorium on wind, a proposal for a statewide plan or some form of carbon tax, this session is sure to be lively.

It’s a good time to reflect on the bold environmental laws passed by Congress in the early 1970s, including the Clean Water Act, Clean Air Act and the establishment of the Environmental Protection Agency.

At that time in Vermont the Gibb Commission — appointed by Gov. Deane Davis to study the causes of and solutions to the “rampant” unguided growth in Vermont after the opening of the interstate highway — issued its report. Within the year its findings were written into a bill, thoroughly vetted and signed into law as Act 250. These actions were wise and swift.

With the stakes so high today, can we hope for the 2013-14 Legislature to pass meaningful environmental law as wisely and as swiftly as its predecessors did in the 1970s?

The following paragraphs, which describe the challenge we face, are adapted from “Greening Vermont: The Search for a Sustainable State,” which I co-wrote with Eric Zencey.

One of the fundamental principles of ecology was offered by John Muir decades ago: “If you try to pick one thing out by itself, you find it hitched to everything else in the universe.” Everything is connected, and a change anywhere in a complex system tends to reverberate through the whole.

Our environmental problems are themselves like an ecosystem, a complex web of interconnection and relation that we don’t completely understand. To address them effectively, the environmental movement will have to “think like an ecosystem” — see, conceptualize and deal with the problematic system as a whole.

Climate change is upon us, and its magnitude is barely comprehensible. Tropical Storm Irene came from a place far from the state, but its causes have roots that extend into our lives and homes. As long as Vermonters burn fossil fuels as if the planet’s capacity to absorb greenhouse gases were infinite, we contribute to the problem. And doing our part to solve the problem will not be enough.

The task can seem daunting. The infinite-planet system has enormous inertia. And like a healthy ecosystem, it is resilient and tends to “heal” itself, absorbing change, adapting, maintaining its status quo. This means that many of the victories of the environmental movement are, indeed, all too temporary.

But there is also an advantage offered by the complexity of the problem: Any action, anywhere, that begins to transform that system will have an effect on the whole. It has leverage points (food, water, energy, transportation, waste streams, economic indicators) at which concerted effort can bring amplified results.

And action can be taken with the assurance that the alternative system of practice — sustainable communities — will eventually out-compete the unsustainable system it seeks to replace.

It’s definitional: An unsustainable system cannot last.

Until its ultimate goal is reached, the environmental movement in Vermont, as elsewhere, will play a much-needed role as it embraces and defines and works for that vision of sustainable communities.

This is the high purpose of civilization in the 21st century, and until that goal is achieved, the main task of the environmental movement will be to ensure that our progress toward it is steady and certain.

In 1970, as the Gibb Commission produced what would become Act 250, its report warned that what was at stake wasn’t just a way of life for a small, rural corner of the United States but nothing less than the survival of mankind.

Action resulting from this report was swift. Forty years later, as we endure the consequences of our irresistible addiction to oil, we see that the Gibb Commission’s warning was not overstated.

Whether we respond as wisely and swiftly to the challenge of climate change remains an open question.

Elizabeth Courtney is co-author of “Greening Vermont: The Search for a Sustainable State” and one of Vermont’s leading environmentalists. Her email is elizabethcourtneyvt@gmail.com.